The present invention relates to safety devices for tractor trailer combinations. More particularly, the present invention relates to safety systems for inhibiting the propensity of a tractor trailer to jackknife under undesirable driving conditions as illustrated in FIG. 5.
Tractors and trailers are conventionally coupled together by a fifth wheel coupler on the tractor in which a kingpin secured to the trailer is pivotally received. The trailer is articulated to the tractor by the kingpin extending from a first plate on the trailer to a second plate on the tractor so as to permit the trailer to rotate or swing horizontally about the kingpin, thereby permitting the trailer to extend at an angle with respect to the line of tractor travel when the assembly traverses curves or turns. This coupling enables the tractor to pull the trailer and provides for relative pivotal movement for maneuvering the vehicle.
One of the problems associated with operation of trailer trucks is the tendency of the tractor and attached trailer to jackknife under certain conditions. Jackknifing occurs when the trailer pivots relative to the tractor to an extent such that the operator can no longer maintain or recover control over the vehicle. Typical driving conditions which may cause jackknifing are those in which the tractor wheels are made to lock and slide or to spin. As shown in FIG. 5, the direction of the vehicle can no longer be controlled, and the vehicle takes the path of least resistance. Improper braking or steering and accelerating or decelerating too fast can all cause jackknifes, especially on roads made slick by rain, snow, or ice.
Many systems have been proposed to prevent or at least to inhibit trailer jackknifing. For example, an assembly of anti-lock or ABS brakes acting on the wheels of the trailer and/or the tractor is employed to prevent jackknifing. The typical ABS system attempts to prevent axle lockup and otherwise to prevent excessive trailer overrunning and consequent jackknifing. ABS systems are rather complicated and difficult and expensive to install, particularly in a retrofit operation because they must be bodily incorporated into the truck's braking system. Moreover, many drivers are leery of ABS systems because they inevitably take a degree of braking control away from the driver. ABS systems also necessarily act between the wheels and the road rather than directly on the trailer and therefore have only a secondary effect on trailer jackknifing.
Many additional systems have been proposed which attempt to prevent or inhibit trailer jackknifing by acting directly on the fifth wheel or elsewhere on the trailer body to prevent or at least inhibit excessive trailer swinging. However, all such systems exhibited marked drawbacks and disadvantages and never gained widespread commercial acceptance. Throughout the years, a number of innovations have been developed relating to anti-jackknife devices, and the following U.S. Pat. Nos. are representative of some of those innovations: U.S. Pat. Nos. 5,690,347; 4,991,863; and 5,456,483.
U.S. Pat. No. 5,690,347 describes a computer controlled braking system including brakes which act directly on the trailer body in response to sensors which detect a jackknifing condition. U.S. Pat. No. 4,991,863 describes a system for preventing jackknifing between a tractor and trailer including blocks formed on the tractor and trailer which prevent angular movement between the tractor and trailer. U.S. Pat. No. 5,546,483 describes a structure for limiting jackknifing including a system of pins which extend from the fifth wheel assembly to project into arcuate slots. Unfortunately, each of theses systems suffer from various disadvantages. For example, prior art systems either require activation of the braking system to occur prior to the safety system being implemented or require continual oversight by the driver. For example, the anti-jackknifing system described in U.S. Pat. No. 5,456,483 initiates when the driver has applied his brakes. Unfortunately, jackknifing can occur even prior to a braking condition such as where a truck is driving on slippery or icy conditions. Moreover, the system described in this patent must be manually deactivated during certain driving condition such as parking.
Thus, there is a significant need for an improved anti-jackknifing system for tractor trailer combinations which does not require continuous oversight by the driver.
There is also a need for an anti-jackknifing system for tractor trailers which is inexpensive to manufacture.
Furthermore, it would be advantageous to provide an anti-jackknifing system that could be employed in new tractor trailers and which could be integrated and retrofit into existing tractor trailers.